Those skilled in the art know that a vehicle has a suspension for connecting one or more wheels to the frame of the vehicle. In addition, it may be desirable, for example, for dump trucks and for trailers in a tractor-trailer combination to have their vehicle carrying capacity increased. Hence, an additional axle and associated suspension, or suspensions, may be utilized to increase the carrying capacity of these vehicles. For ease of use and improved vehicle fuel consumption, it has been found that the additional axle(s) can be lowered into service when needed and, subsequently, lifted from service when not required.
Examples of relevant art involving movable suspensions are as follows. U.S. Pat. No. 6,997,464, teaches a lift axle suspension that comprises a first air bag, a second air bag, and a lever. When an axle is to be lowered, the second air bag is deflated and the first air bag, which is connected to the axle, is inflated so that the axle is lowered. When the axle is to be raised, the first air bag is deflated and the second air bag, which is connected to a first end of the lever, is inflated. In response to the inflation of the second air bag, the lever pivots about a fulcrum to lift the axle which is connected to the second end of the lever.
U.S. Pat. No. 6,398,236 teaches a lift axle suspension with axle reservoir comprising two trailing arms that are pivotally connected to a hanger bracket that is connected to a vehicle frame. An air spring resists rotation of the trailing arms when the axle is in the lowered position. A lift bag, which is positioned between the hanger bracket and the axle, is utilized to raise the axle.
U.S. Pat. No. 6,471,223 discloses an auxiliary lift axle suspension that comprises a hanger bracket that is connected to an inflatable lift bag and pivotally connected to a first end of a trailing arm. A second end of the trailing arm is connected to an air spring. The lift bag, which is connected to another end of the trailing arm, is utilized to raise the trailing arm and an attached axle.
U.S. Pat. No. 6,880,839 discloses a parallelogram lift axle suspension system that includes an in-line lift bellows located between and vertically aligned with a pair of upper and lower control arms so as to provide bi-directional expansion and contraction of the lift bellows. These motions raise and lower the suspension while increasing the space available between the longitudinal frame rails. This results in enabling the use of the suspension in certain vehicles by avoiding interference with other vehicle components of the vehicle located in this space.
European Patent Application Publication No. 0431673 involves an axle lift system for a vehicle where a lift bellows is positioned between a fixed support and a bearing arm, which is connected to an axle. When the axle is to be lifted, pressurized air expands the lift bellows, which causes the bearing arm to lift the axle.
U.S. Pat. Nos. 6,845,989 and 6,416,069 generally disclose a lift axle device that comprises an air spring that is connected on one end to a hanger and on a second end to a trailing arm, which is connected to an axle. When the axle is to be lifted, the air spring is expanded, which in turn causes the trailing arm with axle attached thereto to be lifted.
As detailed above, the relevant art requires various parts that are bulky and in some cases complicated, which tends to add weight and cost. Also, the relevant art makes assembly and replacement of lifting and lowering mechanisms difficult. Further, the art that utilizes bushings at various pivot points may experience an increase in impact loading and fatigue during transport in the lifted position. Thus, a more reliable, compact, lower weight, and a more easily moveable air lift kit has been sought.